Wellington Hospital is concerned about the number of people being admitted after taking the drug known as NBOMe - a synthetic chemical sold to users as LSD.

Wellington Hospital's Dr Paul Quigley says they're getting roughly one person a week coming into the hospital after a bad trip, and they're often hard to handle.

"If they have bad hit with this NBOMe stuff, which is quite common unfortunately, they need to four or five case officers to hold them down and restrain them."

Last year a man was admitted to Christchurch Hospital with cardiac and kidney complications after taking the drug.